1. Field of the Present Invention
The present invention relates to an electronic component device and a method for producing the same, and particularly to an electronic component device that includes conductor films including high melting point metals that are bonded to each other using a low melting point metal, and a method for producing the same.
2. Description of the Related Art
A known method for producing an electronic component device is illustrated in FIGS. 7-1 to 7-4. FIGS. 7-1 to 7-4 illustrate a process for bonding a first component 1 and a second component 2 to each other that are to be provided in an electronic component device. Such a process is described in, for example, Japanese Unexamined Patent Application Publication No. 2002-110726. The first component 1 illustrated in FIGS. 7-1 to 7-4 is, for example, a semiconductor chip as described in Japanese Unexamined Patent Application Publication No. 2002-110726 and the second component 2 is, for example, a substrate on which a semiconductor chip is mounted.
In a stage before bonding the first component 1 and the second component 2 to each other, a first conductor film 3 is formed on the first component 1 and a second conductor film 4 is formed on the second component 2 as illustrated in FIG. 7-1. The first and second conductor films 3 and 4 include high melting point metals, such as Cu, for example. On the first conductor film 3, an oxidation preventing film 5 including, for example, Au is formed. The oxidation preventing film 5 prevents oxidation of the Cu when the first conductor film 3 includes Cu as described above. In contrast, on the second conductor film 4, a low melting point metal layer 6 including a low melting point metal having a melting point less than that of the high melting point metal is formed. The low melting point metal layer 6 functions as a bonding material, and includes, for example, Sn.
In order to bond the first conductor film 3 and the second conductor film 4 to each other, heating is performed at a temperature between the melting point of the high melting point metals defining the conductor films 3 and 4 and the melting point of the low melting point metal defining the low melting point metal layer 6 while arranging the first conductor film 3 and the second conductor film 4 so as to face each other with the low melting point metal layer 6 being interposed therebetween as illustrated in FIG. 7-1. As a result, first, Au defining the oxidation preventing film 5 dissolves in the low melting point metal layer 6, whereby the state illustrated in FIG. 7-2 is achieved.
When the heating is further continued, the high melting point metals defining the first and second conductor film 3 and 4 are diffused in the low melting point metal layer 6 to form an intermetallic compound of the high melting point metals and the low melting point metal. Then, as illustrated in FIG. 7-3, intermetallic compound layers 7 are formed between each of the first and second conductor films 3 and 4 and the low melting point metal layer 6. Then, finally, the low melting point metal layer 6 disappears, and a bonding portion 8 in which the first conductor film 3 and the second conductor film 4 are bonded to each other through the intermetallic compound layer 7 is formed as illustrated in FIG. 7-4.
The low melting point metal layer 6 has a function of compensating for variations in the spacing between the first conductor film 3 and the second conductor film 4. Therefore, the low melting point metal layer 6 must have a thickness greater than a minimum thickness. However, as the thickness of the low melting point metal layer 6 increases, the time required to diffuse the high melting point metal in the low melting point metal layer 6 increases, which results in a problem of reduced productivity.
In contrast, when the low melting point metal layer 6 is thin in order to solve this problem, the ability to compensate for variations in the spacing between the first conductor film 3 and the second conductor film 4 is reduced, which results in another problem of a poor bonding portion being produced.
Moreover, it is known that the intermetallic compound formed in the intermetallic compound layer 7 is relatively hard and fragile as compared to pure metals. For example, intermetallic compounds produced by combining Cu and Sn, Cu6Sn5, Cu3Sn, etc., are mentioned. However, when the diffusion amount of Cu in Sn is not sufficient, Cu6Sn5, which is particularly fragile among the intermetallic compounds listed above, is likely to be produced. When a stress caused by, for example, thermal expansion differences occurs between the first component 1 and the second component 2, the distortion cannot be absorbed, and thus, cracking occurs in a portion at which Cu6Sn5 is produced, which sometimes causes poor conduction.
In contrast, in order to shorten the time required to bond the first conductor film 3 and the second conductor film 4, Japanese Unexamined Patent Application Publication No. 2007-19360 has proposed a method as illustrated in FIG. 8. FIG. 8 is a figure corresponding to FIG. 7-1. In FIG. 8, components that are equivalent to those illustrated in FIGS. 7-1 to 7-4 are designated by the same reference characters, and the duplicate descriptions thereof are omitted.
Referring to FIG. 8, the first conductor film 3 is formed on the first component 1, and a first low melting point metal layer 6a is formed on the first conductor film 3. In contrast, the second conductor film 4 is formed on the second component 2, and a second low melting point metal layer 6b is formed on the second conductor film 4. Then, a metal powder 9 including a high melting point metal is provided on, for example, the first low melting point metal layer 6a. 
To bond the first component 1 and the second component 2 to each other, heating is performed while the first and second low melting point metal layers 6a and 6b are arranged with the metal powder 9 interposed therebetween and then the first conductor film 3 and the second conductor film 4 are arranged to face each other with the low melting point metal layers 6a and 6b interposed therebetween. Thus, the high melting point metal is diffused in each of the low melting point metal layers 6a and 6b not only from the first and second conductor films 3 and 4, but also from the metal powder 9 to form an intermetallic compound. Therefore, the time required to diffuse the high melting point metal throughout the low melting point metal layers 6a and 6b can be reduced.
However, according to the method illustrated in FIG. 8, when the supply amount of the metal powder 9 varies, it becomes difficult to uniformly grow the intermetallic compound from the interface between the first and second low melting point metal layers 6a and 6b. When Cu is used as the high melting point metal and Sn is used as the low melting point metal and the supply amount of the metal powder 9 is not sufficient to form Cu3Sn, fragile Cu6Sn5 is likely to be formed and, due to the same reasons as described in Japanese Unexamined Patent Application Publication No. 2002-110726 above, cracking is likely to occur, which causes poor conduction.